This scene contains all three columnar cacti that occur in the United States. Tall, mostly unbranched saguaros (Carnegiea gigantea) are on the left and middle background, organ pipe cactus (Stenocereus thurberi) in the middle, and fuzzy-topped senita (Lophocereus schottii) in the right foreground. Senita Basin, Organ Pipe Cactus National Monument, Arizona.